A vegetation cutter is a kind of work apparatus for cutting grass or brush growing on the ground. An example of a vegetation cutter is disclosed in JP unexamined patent publication No. 2011-50313 A and in WO 2011/027629 A1, which comprises a frame rod (main pole), a rotary cutter (cutting line) mounted on the front end of the frame rod, and a drive motor (electric motor) mounted on the rear end of the frame rod for driving the rotary cutter. The vegetation cutter is provided with a loop handle on the middle part of the frame rod to be held with the left hand and a grip around the frame rod in the rearward of the loop handle to be held with the right hand by the user while operating the vegetation cutter. The grip is provided with a power switch trigger for energizing the drive motor and also with a safety lock mechanism for rendering the power switch trigger inoperative in the lock position and operative in the release position for preventing the power switch trigger from being erroneously actuated. The power switch trigger is arranged in the lower side of the grip at the position where the power switch trigger is operative by the index finger and/or the middle finger of the user while the user is holding the grip with his/her right hand. The manipulating lever of the safety lock mechanism is disposed in the left side of the grip at the position where the lever is operable with the right thumb of the user.
When the user is to operate the vegetation cutter to cut grass, the user holds the loop handle with his/her left hand and holds the grip with his/her right hand, and, pressing the manipulating lever of the lock release mechanism (herein the “lock release lever” for brevity) with his/her right thumb to release the safety lock mechanism, presses the power switch trigger with the index and/or middle finger of his/her right hand to energize the drive motor to rotate the rotary cutter. As the user keeps the rotary cutter floating a little bit above the ground and swings the frame rod right and left to have the rotary cutter sweep right and left on the grass, the grass growing on the ground will be cut off.
When this type of vegetation cutter is in use to cut grass on the ground, the rotary cutter is kept rotating generally in a horizontal plane and is moved horizontally a bit above and in parallel with the ground. If there is an obstacle like an upright post or a vertical wall of a building on the ground, the rotating cutter should not be moved so close to the obstacle that the rotating cutter may touch it and may be damaged. Thus it was hard to cleanly cut the grass near the obstacle. In order to cope with this situation, the user would direct the rotating cutter vertical to the ground by turning the frame rod circumferentially by 90 degrees thereby to move the rotating cutter along the vertical obstacle to cut the grass near the obstacle. With the vegetation cutter assuming this posture, the power switch trigger is directed sideward and the lock release lever is directed above or below the grip so that the user would hold the grip in a little bit uncomfortable way with his/her right thumb pushing the lock release lever to release the safety lock mechanism and with his/her right index or middle finger pressing the power switch trigger to energize the drive motor.